1. Technical Field
The present invention relates to a lens device interchangeably mounted on a camera body of a cine-camera for motion picture filming or the like.
2. Related Art
Cameras such as cine-cameras are provided with: a lens device having a lens barrel holding a lens system; and a camera body on which the lens device is detachably mounted. In some lens devices, for attachment to the camera body, a bayonet mount ring serving as a connection with the camera body is attached to the lens barrel. In the manufacture of the lens device, when the mount ring is attached to the lens barrel, it is necessary to make an adjustment so that the optical axis of the lens system of the lens barrel and the central axis of the mount ring coincide with each other.
A method is available in which a fixing pin is provided to the lens barrel, a pin hole is provided to the mount ring and the fixing pin is inserted in the pin hole in a position where the optical axis of the lens barrel and the central axis of the mount ring coincide with each other, thereby positioning the lens barrel and the mount ring with respect to each other. However, this method requires that the fixing pin and the pin hole be formed with a high degree of processing accuracy.
An example of a technology where the alignment between the mount ring and the lens barrel can be adjusted after the mount ring is attached to the lens barrel is the one shown in JP-10-115757. JP-10-115757 describes a mount shift device that is provided with a mount frame mounted on the camera body and a lens frame supporting a lens unit and adjusts the position of the lens frame in a direction orthogonal to the optical axis with respect to the mount frame.
When the camera body is replaced according to the purpose for image taking or the like, there are cases where it is necessary to replace the mount ring attached to the lens barrel of the lens device according to the kind of the camera body. For example, in digital cameras, since a cover glass for preventing the adhesion of water drops and dust is incorporated, a mount ring not provided with a cover glass is attached to the lens barrel. On the other hand, in film cameras, since no cover glass is incorporated in the camera body, a mount ring provided with a cover glass is attached to the lens barrel.
The device of JP-10-115757 is not intended for detaching the mount frame from the lens barrel or attaching another mount frame to the lens barrel. When the mount ring of the lens barrel is replaced in cases such as when the camera body is replaced, it is necessary to re-perform the alignment between the optical axis of the lens barrel and the central axis of the mount ring, which makes the work cumbersome.